This invention relates to a process for producing a mixture of thermoplastic polymers suitable for molding purposes, and in particular where one of the components is a polycondensation polymer.
It has long been the state of the molding composition art to vary and improve the properties of a thermoplastic by intimate admixing of an additional polymer. It has also been known to admix the additional polymer in the form of an aqueous latex to the molten thermoplastic (Adv. Polym. Techn. 3:41 et seq. [1983]; U.S. Pat. No. 3,742,093). Only those thermoplastics obtained by addition polymerization processes are cited in the art as molten polymers to which the latex can be admixed. Resins, obtained by polycondensation processes, are not mentioned.
Furthermore, the addition of elastomeric graft copolymers to polyesters has been disclosed (European Patent No. 56,123). The graft copolymers can contain relatively large amounts of water. In order to obviate the danger of degradation of the polyester, the water content is limited to maximally 50% by weight. The use of not dewatered polymerizate latices with a water content of above 50% by weight is neither disclosed or suggested.
This is not surprising since one skilled in the art would know that polycondensation resins, especially in molten condition, are extremely sensitive to water and steam, being subject on contact to decomposition and a marked reduction in molecular weight. (T. Davies in "Chemical Reactions of Polymers" - E. M. Fetters Editor, High Polymers XIX, Interscience Publishers, N.Y., 1964, pp. 533 et seq.; R. Feldmann, R. Feinauer, "Angewandte Macromoleculare Chemie" [Applied Macromolecular Chemistry] 54:1-13[1976]).